A Normal is a line that points in totaly NOT the direction of whatever it is the normal to (???)
For example if a line points straight up and down, (In 2d), then a Normal of that line, is any line that doesnt go up or down at all. ie A left to right line.
In 3d you have a plain. The plane is left, right , forward and backwards. Now ANY line that DOESNOT go either left nor right nee Forward Nor Backwards is a normal to that plain Ie UP and down
For example if a line points straight up and down, (In 2d), then a Normal of that line, is any line that doesnt go up or down at all. ie A left to right line.
In 3d you have a plain. The plane is left, right , forward and backwards. Now ANY line that DOESNOT go either left nor right nee Forward Nor Backwards is a normal to that plain Ie UP and down